This invention relates to the fields of composite yarns, fabrics manufactured therefrom and to tubular, e.g., vascular tissue, prostheses manufactured from yarns or fabrics.
At present there are two surgical methods used in vascular repair. In one method, human tissue is harvested, usually from the patient, and then re-implanted. This necessitates two operations and the difficult handling of tissue. In the other method, vascular repair is achieved with a synthetic tubular prosthesis made from a non-absorbing material such as Dacron (DuPont's synthetic polyester fiber made from polyethyleneterephthalate) or polytetrafluoroethylene (PTFE). These grafts are permanent and sometimes show failure after extended service due to their dissimilarity to natural tissue. These grafts are also limited to repair of larger vessels because of occlusion. Grafts with minimal porosity do not bleed but also do not allow tissue ingrowth. Grafts with high porosity allow tissue ingrowth and formation of a neointimal surface contact with the blood, however, these grafts must be pre-clotted in the patient's blood prior to placement. Some porous grafts with coatings such as albumin have been developed in the hope of encouraging tissue ingrowth.
According to U.S. Pat. No. 4,474,851, the most commonly used fabric for blood vessel prosthesis is made from Dacron produced in several weaves and in combination with other materials. An example of such a material is the DeBakey Elastic Dacron fabric manufactured by USCI, a division of C. R. Bard, Inc. (Cat. No. 007830). Other commonly used materials are said to include felted polyurethane and polytetrafluoroethylene (Berkowitz et al., Surgery, 72, 221 (1972); Wagner et al., J. Surg. Res., 1, 53 (1956); Goldfarb et al., Trans. Am. Soc. Art. Int. Org., XXIII, 268 (1977)). However, it is noted that none of these materials even when specially woven or crimped is able to satisfactorily simulate the elastic nature of natural blood vessel walls (Takabayashi et al., J. Surg. Res., 19, 209 (1975)). Because of this, blood pressure response and blood flow occur differently in natural and artificial blood vessels, and the desirable normal flow characteristics and pressure response are not attained Changes in blood flow are undesirable and often lead to clotting
For disclosures of various known types of vascular prostheses, reference may be made to U.S. Pat. Nos. 4,208,745 and 4,713,070 (PTFE); 4,378,017 (de-N-acetylated chitin and fibrous collagen); 4,474,851 (composite yarn possessing an artificial core fiber, e.g., a polyester such as Dacron, and an elastomeric polypeptide chemically bonded to the surface of the core fiber); 4,718,907 (cross-linked fluorine-containing polymer coatings on a substrate, e g., a fabric manufactured from polyethylene terephthalate); European Patent Application No. 0 202 444 (fibers manufactured from an absorbable polymer, e.g., one derived from trimethylene carbonate, and fibers manufactured from a nonabsorbable polymer, e.g., Hytrel or polyethylene terephthalate); and, PCT Patent Publication No. WO 84/00302 (polylactic acid and segmented polyester urethane or polyether urethane solution deposited upon a PTFE substrate). PCT Patent Publication No. WO 89/01320 describes a soft tissue prosthesis, said to be useful as a vascular tissue replacement, which as a ligament prosthesis possesses a central region made up of a core component comprising a parallel array of elastomeric yarns, e.g., of a spandex-type polyurethane/urea/ether block copolymer, preferably wrapped with layers of Dacron.